Advances in in vitro fertilization and in gene transfer and targeting have now made preimplantation genetic diagnosis (PGD) of embryos, and in the future, genetic modification of embryos, techniques of increasing interest. Because PGD tests for genetic conditions prior to pregnancy, its wide availability could lead to embryo screening for many conditions beyond prevention of severe genetic disease. If combined with techniques for genetic alteration of embryos, it could lead to many more parental attempts to select or control the genetic make-up of offspring. Whether PGD and genetic alteration come to play an important role in human reproduction will depend on improving embryo screening and genetic modification techniques, and on resolving the ethical, legal, and social issues which safe and reliable PGD and genetic alteration would present. The purpose of this project is to produce several professional articles that identify and analyze the ethical, legal, and social issues that surround screening and altering human embryos, thus helping society and relevant decision-makers come to grips with these issues. Year 1 of the project will focus on embryo screening as a form of negative genetic selection, and its use in screening embryos for transfer based on reasons other than avoidance of severe genetic disease, i.e., for susceptibility mutations, for HLA matching, for gender, and for non-medical traits. Year II will then address the ethical, legal, and social issues that arise in positive genetic selection by genetic targeting of embryos. It will explore whether prevailing conceptions of procreative and family liberty include the right of prospective parents to alter or modify the genome of offspring for medical or non-medical purposes.